Gender-specific predictors of retention and opioid abstinence during methadone maintenance treatment

Retention in methadone maintenance treatment (MMT) for 1 year is associated with positive outcomes including opioid abstinence, however, most studies have not investigated gender differences. We hypothesized that predictors of retention and opioid abstinence would differ between men and women, and aimed to determine which factors best predict retention and abstinence for each gender.

Data were available for 290 patients (173 M, 117 F) admitted to outpatient MMT. Regression analyses, stratified by gender, were conducted to identify unique predictors of MMT retention (<1 vs. >1 year) and opioid abstinence rate (proportion of opioid-free urine samples up to 1 year retention).

Gender did not significantly predict treatment retention (mean = 231 days, 39% retained > 1 year) or opioid abstinence (49% overall). For males, significant predictors of > 1-year retention were urine samples negative for opioids (odds ratio [OR] = 6.67) and cannabinoids (OR = 5.00) during the first month, and not cocaine dependent (OR = 2.70). Significant predictors of higher long-term opioid abstinence were first-month urine samples negative for opioids and cocaine metabolites. For females, significant predictors of >1-year retention were first-month urine samples negative for cocaine metabolites (OR = 4.00) and cannabinoids (OR = 9.26), and no history of sexual victimization (OR = 3.03). The only significant predictor of higher opioid abstinence rate was first-month opioid-free urine samples.

These findings indicate gender-specific predictors of MMT retention and opioid abstinence. Future studies on MMT outcomes should examine each gender separately, and consider unique pathways by which females and males adhere to, and benefit from MMT.